Add support for filtering using multi-field indexes correctly

[robertfall]

After becoming more familiar with the way treo emulates IndexedDB using WebSQL I realised that it's probably not feasible to do a proper query when filtering by index with a KeyRange with multiple fields.

I've taken a pass at fixing the testValue function to allow for KeyRanges with multiple fields. I wasn't sure how you run your tests for treo-websql as I assume it doesn't get used when running in PhantomJS. For what it's worth the test suite still passes with this change though as I say, I suspect it's not being used.

[alekseykulikov]

Thanks, man!
I don't have specific tests for treo-websql, I usually just replace it in treo using npm link. The code you provide, looks good and I will run some local tests and release new version on npm.

[alekseykulikov]

all works, treo-websql@1.0.3 contains this fix.

[robertfall]

@lukerandall thanks for your help on this. It's been merge now. ✋ 😃